1. Field of the Invention
The present invention relates to a method for recovering the polyol, which has been supplied for the production of a polyurethane, efficiently by means of a particular decomposing agent.
2. Description of the Prior Art
Recently, organic compounds have been variously discussed as public nuisances and a polyurethane is one such material. Accordingly, various technics for decomposing the polyurethane have been developed.
Almost all technics heretofore proposed rely upon a conversion of the reversible thermal dissociation reaction of a large number of urethane bonds, urea bonds and the like present in the polyurethanes into a non-reversible reaction by addition of amine, dialkanolamine and the like. In general, the main starting materials of flexible polyurethane foams are polyol and tolylenediisocyanate, so that when polyurethane foams are decomposed, the polyol and tolylenediamine and derivatives thereof are formed. The decomposed liquid separates substantially into two layers, the upper layer of which is the polyol and the lower layer of which is the diamines but the diamines are dissolved to a fair extent in the polyol and the diamines in the lower layer form paste, so that the separation of both of the layers is very difficult. Even if both of the layers are separated, it is expensive to purify the polyol by further separating the diamines from the polyol, so that this process is not commercially preferable. Thus, it is quite expensive to reuse the polyol recovered through the decomposition as the starting material for a polyurethane and further when the unpurified polyol is used as the starting material, the dissolved amines act as a catalyst for the reaction system of the polyol and polyisocyanate and hence it becomes difficult to control the reaction in production of the polyurethane polymer.